JP Publication of Application No. H06-156628 (Patent Document 1) describes an example of an article transport facility having an article transport device for transporting articles among a plurality of transfer target locations arranged in the vertical direction. This article transport device includes a vertically movable member which is raised and lowered along the vertical direction, and a transfer device which is supported by the vertically movable member and which transfers an article between itself and transfer target locations. The transfer device includes a support body for receiving and supporting an article, and a projecting and retracting actuator which causes the support body to be projected and retracted between a projected position in which the support body is projected toward the transfer target location and a retracted position in which the support body is retracted toward the vertically movable member.
In the article transport facility of Patent Document 1, the vertically movable is provided with a cushion member which is elastically deformable in the vertical direction. The cushion member is located above the article received and supported by the support members of the fork mechanism (9). More specifically, the cushion member has a spring (16a) interposed between a load stabilizer (11) and a press plate (15) so that the cushion member is elastically deformable in the vertical direction. In addition, the cushion member is configured to be vertically movable between a pressing position in which the cushion member presses down on the article received and supported by the support members of the fork mechanism (9), and an away position in which the cushion member is spaced apart upwardly from the article received and supported by the support members of the fork mechanism (9).
For example, when the vertically movable member is moved vertically, the article can be pressed down on by the cushion member by lowering the cushion member to the pressing position. This prevents the article from being lifted off from the support members, thus reducing the possibility of the article falling from the transfer device. The article tends to be lifted off from the support members due to an upward inertial force especially when the vertically movable member is abruptly stopped during its ascent. However, lifting off of the article can be prevented if the article is pressed down on from above by the cushion member. Therefore, the possibility of the article falling from the transfer device can be reduced even when the vertically movable member makes an emergency stop. In addition, when the support body of the transfer device is projected or retracted to transfer an article to or from a transfer target location, the cushion member can be raised to the retracted position so that the article being transferred would not interfere with the cushion member.
However, in the article transport facility of Patent Document 1, the cushion member needs be raised to the retracted position in order to release the pressing down on the article by the cushion member before transferring (i.e., delivering) the article by the transfer device. In addition, after the transfer (receiving) of an article is completed by the transfer device, the cushion member needs be lowered to the pressing position in order to press down on the article with the cushion member. Thus, since it is necessary to vertically move the cushion member before and after a transferring of an article with the transfer device, somewhat complicated operation needs to be performed in the transfer process.